When a functional fluid is used in applications such as brake fluids or the like, the functional fluid faces problems of corrosion, oxidation, sediment formation, and the like. This is because in many cases, the functional fluid is exposed to a metal surface typically containing copper, zinc, aluminum, and brass and also to a rubber part under extreme conditions such as high temperature. Higher under the hood temperatures in modern cars and trucks, an anti-lock brake system, and longer driving times have created a demand for high-performance functional fluids with better resistance to corrosion, sediment formation and degradation over long periods of use.
A functional fluid typically includes: a base oil formed of a glycol, a glycol ether, esters including, a borate ester and a phosphate ester, an ethoxylated alcohol or a propoxylated alcohol, a hydrocarbon, and the like to which various additives are added to impart resistance to corrosion of various metals, sediment formation, and degradation. In a functional fluid containing triazole compounds, it is known that various compounds are useful as antioxidants, corrosion inhibitors, and the like.
For example, Patent Document 1 discloses an ester composition formed with a major proportion of an ester or a mixture of esters and 0.002 to 2 wt % of amino-substituted 1,2,4-triazole having a specific structure.
Further, Patent Document 2 discloses a functional fluid including a mixture of (a) benzotriazole, a derivative thereof, or a mixture thereof and (b) 1,2,4-triazole, a derivative thereof, or a mixture thereof in an amount effective for suppressing corrosion as well as a base fluid containing at least one kind of compound selected from the group consisting of a glycol, a glycol ether, an ester, and a hydrocarbon (Claim 1).
Further, Patent Document 3 discloses a brake fluid composition in which, to a base fluid for the brake fluid, 0.01 wt % or more of one or more kinds selected from benzotriazoles and derivatives thereof and 0.05 wt % or more of one or more kinds of thiadiazole derivatives each having a specific structure are added.
Further, Patent Document 4 discloses: a hydraulic fluid containing a specific heterocyclic compound for improved corrosion resistance for non-ferrous metals, (Claim 1); and a brake fluid for motor vehicles which contains, as an additional corrosion inhibitor, benzimidazole, tolutriazole, benzotriazole, and/or hydrogenated tolutriazole, together with a heterocyclic compound (Claim 7).
In addition, Patent Document 5 discloses a hydraulic fluid with improved anti-corrosion properties containing (a) 0.05 to 0.0125 mass % of 1H-1,2,4-triazole and (b) 0 to 10 mass % of one or more kinds of other corrosion inhibitors, whereby with the co-use of 1H-1,2,3-benzotriazole and/or 1H-1,2,3-tolytriazole and/or derivatives thereof, the mass ratio of 1H-1,2,4-triazole to the above-mentioned 1H-1,2,3-triazole compounds must be greater than 4:1 (Claim 1).
Patent Document 1: GB 1,111,680
Patent Document 2: JP 2002-536494 A
Patent Document 3: JP 59-157188 A
Patent Document 4: JP 2003-534445 A
Patent Document 5: JP 2004-523641 A